Plasma is a state of matter similar to gas in which at least part of the particles are ionized. The presence of charged particles (e.g. positive ions and negative electrons) makes plasma electrically conductive. A plasma torus is a self-sustained magnetized plasma shaped into a toroidal configuration, with linked poloidal and toroidal (in some cases) closed magnetic fluxes. The extent of linkage of the poloidal and toroidal magnetic fluxes defines a helicity of the plasma torus. Plasma torus contained in a simply connected volume is called a compact toroid (CT). The CT configuration can include, for example: (i) a spheromak configuration that exists close to a stable magnetohydrodynamic equilibrium with an internal magnetic field having both toroidal and poloidal components; or (ii) a Field Reversed Configuration (FRC), which also has a toroidal magnetic topology, but can be more elongated in the axial direction with an outer surface being similar to a prolate ellipsoid, and which has primarily a poloidal magnetic field, with no toroidal magnetic field component. CT plasmas can be formed in a range of magnetic configurations, including ones that exist in states that are in between spheromak and FRC states. It is also possible for an initial plasma torus to evolve and change its magnetic configuration during time.